Cut off under WOT after installing downpipe?

[nelsonmxmarc]

Up until now, ive had no real issues, but today has been a handful!!

..Drove the car last night to my shop - Ran perfect, literally, under 15-16 lbs of boost @ 4 celsius, mint, no hesitation nothing..

Today, i installed my 3" split dump/downpipe with divorced wastegate to stock cat (for noise restriction ) to 3.75", no resonator, and ends with an HKS super dragger.. Also reused my oem EGT and installed a UEGO (before cat).

Took the car for a quick rip with only the downpipe because it sounded unbareably mean.. Noticed it back fired like there's no tomorrow; pop pop pop pop UNDER ACCEL. up until 4k. Never floored it to WOT because i was kind of worried.. Go back and install rest of exhaust..

......STILL DOING IT??

1. Normal driving, everything is perfect. AFR's are great etc.

2. My stock boost is now 15.9 psi.. EBC is off and peaked @ these numbers.

3. My AFR under WOT is 10.8-11.4 (decent)

4. I lose complete power at 5000 rpm under wot, right after turbo spools HARD.

6. New plugs (1.1mm though..) , compression is 141 across the board.

7. all ive done is installed a downpipe, fixed a massive exhaust leak, and removed the resonator..

What should i be looking for?? I was thinking vac leak but under WOT at any rpm it should shudder and show signs.. My car is literally just cutting out.

Also, the car continuously back fires, as if its over fueling. Everytime i shift, it backfires, everytime i floor it, it pops a bit then picks up.. I'm really confused!!!

Fuel cut off? ECU in safe mode? Maf not sufficient (stock) ?

ECU Was reset - no change.

[BrianV8]

Tighten your plug gap up to .8mm sounds like when u got more flow u got a hair more boost and might have been just enough to make the difference to start blowing out your spark. Try that first, quick easy fix. Good luck

[nelsonmxmarc]

It seems strange though considering i've been running a pretty consistent 15-16 lbs boost with my stock setup.. I never realized swapping the downpipe would account for such a spike in pressure.
Oh and the money will be on it's way at the beginning of next week! Unless of course i blow my motor in the midst of this trouble shooting

[nelsonmxmarc]

Also, as they're the iridium ngk (forget the part # off the top of my head)... is there a special way to gap these? I've always been shunned from doing so as its tend to damage the electrode?

[BrianV8]

Well usually increaing flow on the intake and exhaust changes boost a tiny bit, could be fluke, either way 1.1mm on that much boost is pretty big gap. My coils get tired, i have to run a .7mm gap to keep the spark going.

[nelsonmxmarc]

Thanks Brian! Appreciate the help; let me make a pot of coffee and head over to the shop and see what i can do

[BrianV8]

haha no worries man, i've scene that kind of problem around here a lot, hope it works out for you.

[Zacho]

What heat range are the plugs?

I had a similar issue running bkr6e above 12 psi, hit a brick wall. I was informed bkr7e's would be better and right after I hit that wall the 1st time I put in some bkr7e's (pre gapped .8) and it went away and was totally fine up to 1.1 bar(as far as I took them). They are pretty cheap for a set of 6 if you just want to test before you go changing the gap on more expensive plugs.

I've used the champion plugs from can tire for the 2jzgte gapped down to .8 in a pinch as well.

[BrianV8]

ya thats a very good point too!!!! forgot about that. Hot plugs will cause that. I run autolite plugs, really nice cold plug.

[M13]

you need colder, closer gapped plugs.

[klys]

your spark plugs are to blame, gap them asap as said before!

a regular tool will do. like 5-9$ at canadian T

watch out for your fuel cut... since your exhaust is now alot less restrictive, you may still boost at the same pressure, but your moving alot more air earlier which mean you may hit your fuel cut, it can happen at WOT and 5000rpm...

we could do a consult run next week to see how everything is behaving if you like

[nelsonmxmarc]

Thanks guys!! Gapped to .8 mm now, just about to go for my first test. Started up and idles much smoother at this weather.. I'll keep you posted!

Thanks Marc-Andre, that'd be amazing!

[nelsonmxmarc]

Plug gap solved the popping / back fire dilemma, so that's amazing, thanks guys!

Pulls 1st,2nd,3rd to redline @ 14.5 STOCK psi. (EBC is off)

however, in 4th, which makes sense; it hits 14.7 and falls flat on its face with a perfect AFR @ 6000 rpm sharp. THUS, im assuming boost cut (Fuel and ignition) from the ECU (stock ecu..).. It's getting a retune in the spring, however is there any way at all i can run the car at it's full potential and overlook this ecu cut, or am i going to have to wait til that's tuned out?.. I haven't played with the boost controller to fool the actuator, but even then, stock is hitting around 15 lbs so anything i do above that will fall flat on its face regardless..

Oh well!

[BrianV8]

The boost cut gets tuned out. I really hope you have a wide band watching your air fuels when your cranking the boost that much with the stock ecu!!!!. If your interested over the winter my business partner does ecu socketing. If you sent us your ecu we can pull out the factory eprom chip, put a socket in, and if you want to get another base tune going for your supporting mods shadybeaverguy can hook you up with a tune to get you started. Pop one of his chips in the socket and your good to go.

[nelsonmxmarc]

Thanks Brian! However I believe I'm going to go with nistune and have it
dynoed at Almasi in the spring. I have an aem uego and have always seen great afrs. Oh well, almost winter anyways!